Many optical and/or electrical devices comprise a chamber defined by multiple components, with additional optical and/or electronic elements housed and protected inside the chamber. Hermetic sealing of such chambers of such devices may be desired depending on the included components to extend the life span of the device. Hermetic sealing can be a challenge.
For example, OLED (organic light-emitting diode) display is on the horizon of next generation display market, but hermetic sealing technology becomes one of the hurdles for its commercialization. The diodes are in general very sensitive to oxygen and moisture. Thus hermetic sealing is required for the chamber housing them. Various frit sealing methods have been developed to join and seal glass plates to form such hermetic chambers. One exemplary method utilizes electromagnetic irradiation, such as an infrared laser beam, to heat and soften the frit material to achieve the hermetic sealing.
Another method involves direct resistive heating of the frit materials to achieve a bonding of the components to be sealed together. United States Patent Application Publication Serial No. 2007/0096631 and U.S. Pat. No. 7,282,393 disclose direct resistive heating of frit materials to join two substrates. However, the direct resistive heating approaches as disclosed therein suffer from various drawbacks and need improvement. One of the drawbacks is non-uniform heating of the frit material between the substrates, which can lead to stress and crack formation in the seal, and possibly delamination.
Frit sealing of devices having an enclosure with a large area, such as flat panel TV based on OLED display, poses significant technical challenges. Traditional frit sealing using a layer of frit material between the large base substrate and the cover substrate as the bonding agent and the physical spacing component cannot be used effectively for such large sizes. The bonding strength and the separation can both fall short. Sagging of the glass substrates can cause unwanted contact between the cover plate and the substrate bearing electronic components.
The present invention provides a direct resistive heating method capable of achieving a robust hermetic sealing for large size devices.